Threaded fastener



E. M.` GRE`EN 2,353,030

` THREADED FASTENER Filed Feb. 9, 1945 INVENTOR. BY'MMET M 6955A/ rroRNEYs Patented July 4, 1944 UNITED STATES PTENT OFFICE THREADED FASTENER Emmet M. Green, Los Angeles, Calif.

Application February 9, 1943, Serial No. 475,267

7 Claims.

This invention relates to threaded fasteners and more particularly to an improvement in Vthreaded fasteners of the' kind having the characteristics of both a screw and a rivet.

` An object of the invention is to provide an improved fastener of this kind having a strong 'and rugged thread of novel form enabling the fastener to` be used satisfactorily for both light and heavy duty.

A further'object of the invention is to provide a fastener of the character mentioned in which the thread has a blunt or rounded upper end spaced from the head to form a backout-arresting shoulder for effectively preventing reentry of the thread in the work opening when the fastener has been fully driven, and in which the thread increases in width toward said blunt end so as to strengthen the thread and facilitate its passage through the work.

Other objects and advantages of the invention `will be apparent from the following description when taken in conjunction with the acompanying sheet of drawings in which Fig. 1 is an elevation of my improved fastener showing the same on an enlarged scale;

Fig. 2 is an elevation showing a completed assembly or fastening utilizing my improved fastener;

Fig. 3 is a view similar to Fig. 2 but with the fastener rotated through 90 and with the work pieces shown in section;

Fig. 4 is a transverse sectional view taken through the fastener as indicated by line 4-4 of Fig. l; and

Fig. 5 is a developed plan view of the thread of the fastener.

Before proceeding with a more detailed description of -my improved fastener, it is well to point out in a general way that my fastener can be used for a variety of different purposes and particularly where two or more plates or other parts are to be permanently connected or fastened together. It is especially useful for attaching or fastening purposes where one side of the work is inaccessible to wrenches or riveting tools. As will be explained mo-re in detail herein, my fastener is adapted to be screwed into the work and embodies a backout-arresting means which effectively prevents removal of the fastener from the opening of the work when the fastener has been fully driven.

As shown in Figs. l and 4, my improved fastener I D comprises a stem I I `provided at its upper end with a head I2 and carrying one or more helical threads I3, in this instance two such threads spaced 180 apart and each of which extends through approximately 360 or slightly more than 360. The head may be of any desired shape or form, and in this instance is shown as being a round head having the usual screwdriver slot I4 therein and having a substantially at undersurface I5 forming a work engaging face or shoulder.

nIn Figs. 2 and 3` I show my fastener I0 applied to a pair of plates or elements I6 and I1 which are to be permanently connected. The outer work piece I6 has a preformed opening I8 therein and the inner work piece I'l has a preformed opening I9 substantially aligned with the opening I8. These openings are preferably of a size only a little larger than the diameter of the stem II. When the fastener is applied to the work piece it is rotatively advanced through the preformed openings by causing the threads I3 to cut or indent thread grooves I8a and I9a in the walls of the openings I8 and I9 during their passage through the work.

As shown in the drawing, the upper ends 20 of the threads I3 are spaced from the head I2 and are provided with enlargements forming backout-arresting shoulders 2I which engage the inner surface of the work piece II when the fastener has been fully driven and which cooperate with the surface I5 of the head for clamping the work pieces together in permanently connected or riveted relation. The upper thread ends 20 are of blunt or rounded form so that reengagement of the threads in the opening of the work will not take place even though an attempt is Amade to unscrew the fastener from the work. The axial distance which the shoulders 2I are spaced from the head I2 is usually dependent upon the thickness of the work and is preferably .such that when the surface I5 of the head is in engagement with the outer surface of the plate or element I6 the shoulders will be in the above described clamping engagement with the inner plate or element I1.

In accordance with the present invention, the threads I3 are so formed that they increase in width from their relatively sharp lower ends 22 toward the head I2 and are of maximum width at their blunt or rounded upper ends 20. The upper and lower helically extending faces 23 and 24 of the threads are sloping or beveled faces and at the lower ends of the threads these faces meet or converge to give the initial section of the threads a V-shape with a relatively sharp top edge which affords easy starting of the fastener in the opening of the work piece Il. The height of the threads increases progressively for the length of this relatively sharp initial or starting section until the full thread height is reached at the point 2l. From the point 2l to the upper end 20 the thread height remains substantially constant but the thread width increases progressively and the width of the lat tops 28 of the threads increases correspondingly from the points 21 to a maximum width at the blunt upper ends 20. As shown in the drawing, the beveled upper faces 23 of the thread convolutions are carried across and around the upper thread ends 

